There are articles of manufacture that are made using two facing metal sheets with an interposed layer of relatively soft and flexible polymeric material. The sheets may be of the same or different metal alloy composition. Sometimes the interposed polymer layer is an adhesive for bonding the metal sheets in a sandwich-like assembly. While the adhesive joins the sheets, it may also provide a corrosion resistant layer when the sheets are of different composition. In other applications the polymer layer may be a viscoelastic material for providing sound and vibration damping properties to the laminated metal sheet assembly.
Often it is desired to supplement whatever adhesion is provided between the sheets by the polymer layer to prevent them from peeling apart when the layered sheet structure is handled or formed. Resistance spot welding and rivet bonding are two methods of joining sheets that have been laminated for sound deadening or for increasing the resistance to peeling of adhesively bonded sheets. Each of these joining methods has disadvantages, and it is an object of this invention to provide an alternative method of providing bonds between facing metal sheets separated by a polymer layer. Furthermore, it is an object of this invention to provide an improved method of bonding a metal-polymer-metal laminate to a solid metal article or of bonding two metal-polymer-metal laminates.